This proposal builds upon and expands our 20 year longitudinal research program investigating languaged changes in normal aging and dementia. Throughout our research program, a major theme has been to understand the relation between changes in language function and changes in non- language cognitive functions. That theme continues to motivate the current set of studies. A second theme has been the investigation of a specific conceptual mechanism that may partly explain the lexical retrieval deficit seen in normal aging. This mechanism posits an age- related deficit in the transmission of information from semantic to lexical-phonological nodes within the semantic memory network. A. Core Longitudinal Project: We propose to investigate relations between lexical retriecal skills and both linguistic and non-linguistic cognitive factors. We continue to administer an extensive battery of language and non-language neuropsychological cognitive factors.We continue to administer an extensive battery of language and non-language neuropsychological cognitive tests to the same individuals tested up to four times previously. We use the new data to test whether lexical retrieval deficits can be predicated by earlier performance. B. Semantic Knowledge in Alzheimer's disease: This project investigates performance over time in subjects with AD, using both an automatic semantic priming task and several off-line measures of semantic memory. We test whether contradictory priming findings in the AD literature may be explained by changes in patterns of performance over time within individuals who have AD. C. Role of Working Memory in Language Comprehension of the Elderly: We propose to extend our earlier work on the auditory comprehension of sentence-level discourse by exploring the relation between traditional measures of "working memory" and meaures of linguistic comprehension. We test the hypothesis that changes in comprehension performance associated with aging reflect declines in individual working memory capacity. D. Phonological Factors in Lexical Retrieval Failure Associated with Aging: We expand our consideration of mechanisms underlying the lexical retriecal deficits associated with normal aging. Using a picure-word interference paradigm and either semantically-related or phonologically - related word primes, we test the whether facilitation from phonological primes in a picture naming task is reduced in aging. E. Relation Between Lexical retrieval Failure and Perseveration in Normal Aging: We induce perseverative behaviors in normal subjects by using a modified version of a common speeded naming task. We test whether subjects with poor naming performance on a confrontation naming task will have higher rates of perseveration on the speeded naming task.